Structural degradation of concrete structures due to corrosion of the reinforcing steel is one of the most extensive durability problems facing concrete structures. This gives rise to concerns about structural safety, integrity, and serviceability. As a result, monitoring the corrosion of the steel reinforcement in the concrete structures is greatly desired so as to detect the state of corrosion of the reinforcing steel in these concrete structures thereby being able to address the corrosion through preventive remedial measures and economic repairs before it leads to severe structural damage or failure. By being able to implement preventive remedial measures prior to severe structural damage or failure, the overall life-cycle costs in maintaining and repairing the concrete structures will be lower than the cost of rehabilitating such structures after the point of severe structural damage or failure.
Monitoring this corrosion is difficult though since the embedded steel is not visible to the naked eye. Furthermore, detection techniques are needed to indicate initiation of corrosion so that remedial action can be taken before the damage is irreversible. Detection techniques, such as acoustic, ultrasonic and radar, have proved to be limited in this capacity.
Conventional corrosion monitoring techniques, such as half-cell potential and linear polarization, provide instantaneous measurements which are highly subject to the conditions (e.g., moisture, temperature) during measurement. Alternatively, sensors that are placed within the concrete structures using a sacrificial corroding element provide the most direct measurement of corrosion. However, obtaining this data requires electrical access, such as by wire, to the sensor. Any methods that require running wires breach the concrete and provide an ingress point for corrosive agents.
As a result, monitoring the corrosion of the steel reinforcement in concrete structures without breaching the concrete, such as by running wires, would greatly advance the ease and accuracy in measuring the corrosion. Furthermore, given the need for long-term monitoring of these concrete structures, such monitoring devices should be battery-free, cost effective, durable and reliable.